The present invention is related to medical devices and, more particularly, to medical devices for monitoring fluid retention levels in a patient during a medical procedure.
Fluid management is crucial in many medical procedures. Oftentimes, a patient is exposed to relatively large volumes of saline or other perfusion fluids. In some procedures, fluid is introduced into a patient's body to flush out impurities (e.g., dialysis). In other procedures, fluid is introduced into a patient's body to act as a distending medium. During these procedures, excessive fluid retention by the patient may be dangerous and even fatal.
As an example, electrosurgical procedures such as hysteroscopic endometrial resection and transurethral resection of the prostate require the use of a non-conductive irrigant fluid as a distending medium. Excessive absorption of the irrigant fluid by the patient can be detrimental so it is important for the operating room staff to keep track of how much fluid has been absorbed by the patient.
In order to monitor fluid levels, many irrigant bags are prefilled by the manufacturer or include fluid level markings. The operating room staff may attempt to keep a running estimate of how much fluid has been absorbed by the patient according to the difference between the volume of fluid in and the volume of fluid out. However, in addition to the possible human error, the irrigant bags routinely do not provide an accurate volume measurement as the manufacturer may overfill the irrigant bag or the fluid level markings on the bag are not appropriate for precise measurement. Therefore, this method of measuring patient fluid level retention is inaccurate and results in low physician confidence.
Other known fluid retention management systems are based on measuring the rate of fluid flowing into the patient and the rate of fluid flowing out of the patient. However, small errors in the measured rate can produce large errors in the total fluid retention over time. Therefore, this approach does not provide an accurate measurement of fluid retention of a patient.
During certain endoscopic surgeries, especially therapeutic hysteroscopic or urologic procedures, considerable volumes of irrigation fluid must be infused into and recovered from a patient in order to ensure good visibility and proper distension of the cavity being viewed. Typical endoscopes operate at flow rates of more that 500 ml per minute. Typically, fluid irrigant bags range from 1 to 3 liters and collection canisters are not larger than 3 liters. Therefore, every few minutes, the circulating nurse must change a collection canister which involves becoming contaminated with bloody fluid. The nurse must then rapidly change gloves so that an irrigation bag may be changed.
Under this scenario, the nurse is continuously occupied with fluid management and is required to lift heavy irrigation bags overhead and stoop to change heavy collection canisters. In addition, the nurse has to constantly be aware of the fluid deficit status in order to keep the physician apprised of any excessive (e.g., more than 1.5 liters) fluid absorption by the patient.